Animal litters, such as those used in containers placed in designated sanitary areas, cages, exercise areas and the like for animals such as pets, e.g. cats, dogs, birds, guinea pigs, rabbits, mice, gerbils, monkeys, reptiles, poultry, etc. are well known in the art. These litters are generally used to accept the excrement, urine and feces, of the animals, in lieu of the animals relieving themselves out of doors for various reasons, including, but not limited to compliance with the leash laws, the safety of the animal, etc.
Litter materials have comprised a wide range of substances, including, but not limited to, dried grasses, e.g. hay, alfalfa or straw; husks; sawdust; corn cob grits; excelsior; wood shavings; cereal hulls; cotton; bark; lignocellulose; cellulose; ground sugar cane; shredded paper; cloth; silicates; sulfates; mineral compounds, e.g. porous inert solids such as clays, even burnt expanded clays; sand; particulate, absorbent organic polymers, such as polyethylene, polypropylene or polystyrene; and the like. It is also known to modify litters for various purposes, such as to reduce the odor of the animal excrement, or to cause agglomeration of the litter to facilitate its easy removal from the box, cage or the like to avoid waste by having to remove the unused litter along with the used litter requiring disposal. It is also known to provide chemical indicators in animal litters for a variety of purposes, such as to indicate the necessity of litter removal or to provide information about the health of the animal using the litter.
For example, U.S. Pat. No. 3,059,615 teaches an acidified cellulosic litter with a pH of substantially 2.5 to 3.5 and a neutralization capacity of at least 2, where the neutralization capacity is based on attaining a pH of no higher than 6.5. The acidified litter is thus an indicator which changes color at the indicated pH to serve as a warning that it is time to change the litter. The acids and bases used are simply contacted with and physically absorbed into the cellulosic litter.
A litter package having a body of litter within a container of waterproof material for use by a pet after the package has been opened to expose the litter substantially throughout the area of the container when disposed for use is disclosed in U.S. Pat. No. 3,978,818. The litter body consists of particles of absorbent material or materials that are chemically neutral when wet. Testing means are associated with the litter and of an indicator type changing color if wetted by urine containing a color-changing reactant indicating an unfavorable health condition. The testing means may be incorporated in litter material, carried out on the inner surface of the container or on inserts when the package is open. The testing means includes at least one unitary portion under each position the animal may occupy while urinating and of an area such as to become wetted at least in part by contact with urine-wetted particles in the normal use thereof thus to be subject to the reactant throughout a predetermined time. The indicating means may include different types of indicators, each changing color in response to different reactants, the colors being different for each reactant. Again, the indicators are simply sprayed onto and are physically absorbed by the shredded paper litter used.
U.S. Pat. No. 4,020,156 describes fragrance releasing crystal beads that gradually release a fragrance under anhydrous conditions and provide a rapid release of fragrance when wetted. The beads comprise a water-soluble particulate carrier, e.g. prilled urea, coated with a finely divided highly absorptive inorganic matrix containing the fragrance. The beads optionally include emollients and bacteriostats and the like and can be used for pleasingly perfumed sachets or as bath beads or as agents for the control of malodors in pet litter. The particulate beads may be conspicuously colored such that their color substantially disappears as they are dissolved, giving a visual indication of the need for replenishment.
The use of a finely divided calcium hydrosilicate material, in particular aerated or foamed concrete, as a substance for binding and clearing of urine and excrements of the kind excreted by pets is mentioned in U.S. Pat. No. 4,315,761. The material gives rapid and effective drying of the excrements, which, particularly if the material is combined with gypsum as a bond-improving agent, becomes extremely easy to remove or clear. The calcium hydrosilicate and the gypsum are simply mechanically mixed together.
U.S. Pat. No. 4,638,763 teaches the use of anhydrous sodium sulfate as an additive to animal litters formed from mineral, cellulosic, or chlorophyll-containing base materials. The amount of anhydrous sodium sulfate added is from approximately 0.5 to 4 parts for each 100 parts of the base material of the litter formulation. Additionally, an additive composition can include approximately 1 part citric acid for each 10 parts, by weight, of anhydrous sodium sulfate, approximately 1 part sodium chloride for each part of citric acid, by weight, and smaller amounts of activated carbon granules and germicidal agents. Again, the components are simply physically mixed. The additive upon absorbing the urine apparently forms a deposit of sufficient size and strength to be removed by a sieving spoon along with the feces or urine.
Finally, an animal litter comprising a porous, inert solid substrate and a dry particulate polymer is mentioned in U.S. Pat. No. 4,685,420. When animal urine contacts the animal litter there are produced gelled agglomerates containing the animal urine, polymer and solid substrate. The gelled agglomerates have sufficient mechanical integrity to be conveyed as discrete entities thereby permitting animal urine to be physically removed from a litter box containing the animal litter of the '420 patent invention. Suitable polymers include, but are not limited to polymers of acrylic acid, methacrylic acid, and alkali metal salts thereof.
An unresolved problem with animal litters containing physically absorbed chemical indicators that are used to provide a visual indication of an animal's health is that once the reaction occurs and the color is produced, prompting action on the part of the animal owner, the veterinarian cannot regenerate the color from the litter to be useful as a diagnostic tool. The veterinarian thus must rely on the sometimes inaccurate recollection of the owner, or must express urine from the animal in question in a sometimes unsuccessful attempt to recreate the visual indication.